The present invention relates to a new, novel and distinct variety of Prunus rootstock, (P. dulcis×P. persica), and which has been denominated varietally as ‘Cornerstone’.
The present variety of rootstock resulted from an on-going program of fruit and nut tree breeding. The purpose of this program is to improve the commercial quality of available deciduous fruit and nut varieties, and rootstocks, by creating and releasing promising selections of prunus, malus and regia species. To this end we make both controlled and hybrid cross pollinations each year in order to produce seedling populations from which improved progenies are evaluated and selected.
The seedling ‘Cornerstone’ was originated by us from a population of seedlings grown in our experimental orchards located near Fowler, Calif. The seedlings, grown on their own roots, were the result of a controlled cross made in 1987, of the unpatented almond tree ‘Titan’, which was used as the seed parent; and an unpatented peach tree ‘Nemared’ which was used as the pollen parent. The seedlings resulting from the cross were then planted into an experimental site known to contain high populations of nematodes which are a major pest problem for commercial plantings of prunus plant material. One seedling, which is the present variety, exhibited especially desirable characteristics, and was marked, ‘677RS’ for subsequent observation. After the 1984 growing season, the new, present variety, was selected for advanced evaluation and repropagation.
The new seedlings (approximately 50) resulting from the aforementioned cross were then later planted into an experimental site known to contain high populations of root knot nematodes (Meloidogyne javanica and Meloidogyne incognita) species, and grown for one year. These two nematodes can be a major pest effecting commercial rootstocks and are commonly found in the sandy soils of the Northern, Central and Southern San Joaquin valleys of the California interior. These seedlings were planted in December of 1988 and removed in January of 1989.
Of the approximately 50 seedlings that were subjected to the root knot nematode planting, 3 seedlings were later identified as having no root galling from the root knot nematodes, and further had an absence of galls from agrobacterium tuberfaciens. These same promising seedlings exhibited well advanced root development and an adequate tree vigor. Further re-propagations and evaluations showed that the seedlings exhibited a significantly low incidence of crown gall. Moreover, one of these three seedlings exhibited a purple-green leafed character (commonly referred to as red leaf), and as such was selected for further repropagation, testing and evaluation to determine if this rootstock might impart these same characteristics to scion varieties when compared to the rather common ‘Nemaguard’, ‘Nemared’ and Titan (all unpatented) or ‘Hansen’ 536 (U.S. Plant Pat. No. 5,173) commercial rootstocks. Subsequent evaluations have confirmed that these same subsequent characteristics have been passed on to subsequent re-propagations of trees.